Since diode-lasers were developed to deliver enough power to mark a laser-radiation sensitive medium with a short pulse delivered from a diode-laser, several printing or marking arrangements using diode-laser sources have been conceived, and some have been commercialized. In all such printers or markers, it is necessary to scan a laser-beam, modulated according to image information, over the laser-radiation sensitive medium to form an image on the medium. Various scanning methods have been proposed or implemented. These range from scanning using a two-axis galvanometer arrangement to scan over a stationary medium, to translating a laser-beam repeatedly over a moving medium.
In certain moving-medium implementations, the medium is moved linearly by a tape transport or drum with the laser-beam translating in the direction of motion. The medium is usually moved incrementally (row-by-row). In other moving-medium limitations the medium is rotated while supported on a disc with the laser-beam translating radially over the disc-supported medium.
One measure of performance of a laser printer or marker, image quality being equal, is the speed with which an image is produced. Related to this is the speed with which a laser-beam can scanned across a medium. In a galvanometer scanning device, scan speed is limited primarily by available power in the laser-beam, as galvanometer scanning itself can be extremely rapid. In other schemes where the laser-beam is scanned mechanically, using a translating platform on which a laser and focusing optics are mounted, or using a translating platform on which optics are mounted with remote delivery of the laser-beam to the optics, the image production speed can be limited by the speed at which the platform can be translated.
U.S. Pre-Grant Publication No. 20100079572 describes a laser printing arrangement wherein a laser-sensitive medium in tape form is moved incrementally in the length direction of the tape, and a scanner head is translated perpendicular to the length direction of the tape. The scanner head includes a scanner which scans a laser-beam in one-dimension (the length or motion direction of the tape) only. The scanning allows a plurality N of image rows, for example about ten, to be printed in one translation of the scanner head. This cuts down on the scan-head translation-speed needed by a factor of N. This also permits the tape to be incremented one every N rows compared with once every row in a non-scanning arrangement.
While the arrangement of the '572 publication provides a solution to the above discussed translation-speed problem, it still involves the use of a scanner. Scanners, even one-dimensional scanners, can be relatively expensive items, particularly if they are to be made reliable enough to withstand mechanical forces encountered as a result of translation in translating scanner-head. Such forces can be relatively high on direction changes of the scanner-head. There is a need for a laser printer arrangement for printing using a translating print-head that can achieve higher printing speeds without the need for a correspondingly higher translation speed, and without the need for a scanner device of any kind.